Many medical devices adapted for implantation also have high power requirements and must be frequently connected to external power sources. Inductively coupled transcutaneous energy transfer (TET) systems are increasingly popular for use in connection with these high-power implantable devices. A TET system may be employed to supplement, replace, or charge an implanted power source, such as a rechargeable battery. Unlike other types of power transfer systems, TET systems have an advantage of being able to provide power to the implanted electrical and/or mechanical device, or recharge the internal power source, without puncturing the skin. Thus, possibilities of infection are reduced and comfort and convenience are increased.
TET devices include an external primary coil and an implanted secondary coil, separated by intervening layers of tissue. The primary coil is designed to induce alternating current in the subcutaneous secondary coil, typically for transformation to direct current to power an implanted device. TET devices therefore also typically include an oscillator and other electrical circuits for periodically providing appropriate alternating current to the primary coil. These circuits typically receive their power from an external power source.
TET systems commonly include an implanted controller that can be used to monitor and control any implanted devices. If a fault is detected in the implanted device or another component of the TET system, there is a need for the controller to notify the patient or a nearby healthcare professional.